This relates to integrated circuits, and more particularly, to circuitry for integrated circuits that can be used to improve performance and reduce power consumption by selectively overdriving pass transistors.
Integrated circuits such as programmable integrated circuits often contain volatile memory elements. Typical volatile memory elements are based on cross-coupled inverters (latches) and are used to store data. These volatile memory elements are often used to store configuration data. Programmable integrated circuits, in particular, can be customized in relatively small batches to implement a desired logic design.
The memory elements in a programmable logic device produce static output signals that reflect the configuration data that has been loaded into the memory elements. The static output signals drive the gates of n-channel and p-channel transistors, which are often used as pass transistors and are incorporated into multiplexers and other logic components. Depending on the current application of the programmable integrated circuit, it may be desirable to operate the pass transistors in a high speed mode or in a low power mode.
To accommodate operation in both the high speed mode and the low power mode, some integrated circuit designs use body biasing arrangements in which the bulk or body terminals of certain transistors in the circuit are biased to adjust the transistors' threshold voltage. For example, bulk voltage adjustments that decrease the transistors' threshold voltage may place the integrated circuit in the high speed mode, whereas bulk voltage adjustments that increase the transistors' threshold voltage may place the integrated circuit in the low power mode (i.e., by reducing leakage).
Although techniques such as these help to reduce power consumption while preserving device performance, it is not always possible to bias the body terminal of transistors in active circuits.